This quote from Carl Sagan in The Demon-Haunted World has always stuck with me. It applies to many circumstances, including the one of the profile questions on this site. They make assumptions about the nature of belief that are not held by everyone--especially when selecting for the demographic of this site. Asking me questions of "do you believe in X?" is inherently assuming that my world view is governed by belief. I choose to construct my world view based on evidence. For things for which there is no evidence, I could be asked to speculate, but it would be just that--speculation, not belief.
Do you share my approach to my relationship with reality?
You have to believe the evidence though and which evidence you choose to believe will shape your worldview.
In my field of physics, for example, we get all manner of evidence popping up all the time. And if I choose to believe it physics goes one way; if we dismiss it another.
Consider Dark Matter. We choose to believe the evidence for it and come up with all manner of physics to explain and support a universe with it. However, there are many people that don't believe the evidence for it and come up with all manner of physics to explain and support their universe without it.
Consider Aliens. There is no good evidence that aliens exist and thus some people are "agnostic" about aliens: no proof of aliens exists. On the other hand, people cite the planets being found and the vastness of the universe as evidence that they do exist... they are "believers" when it comes about aliens: aliens absolutely exist. Two worldviews, same universe, different view of what evidence means, different perspective guided by evidence.
Belief is important in some contexts. The Declaration of Independence is one example of a document where very pragmatic men expressed certain normative beliefs.
I believe that there are unidentified flying objects. Every time I see an object suspended in or traveling through the air and I can’t make out what it is I tell myself “Eureka!” in Spanish and chalk one more UFO sighting into my own personal collection.
I don’t believe in god because, unlike UFO’s of the sort that I’ve described and which I have seen and expect to continue seeing all the time, I have never seen god. And from the description that the people who claim to have seen god provide, I’m certain that if god existed there would and could be no question about it. It just makes no sense to me that such a powerful being would spend an eternity playing hide and seek with us.